From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-16.5 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_CR_TRAILER,INCLUDES_PATCH,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 3448CC4338F for ; Mon, 2 Aug 2021 13:07:21 +0000 (UTC) Received: from lists.gnu.org (lists.gnu.org [209.51.188.17]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPS id CE4EB60F6D for ; Mon, 2 Aug 2021 13:07:20 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.4.1 mail.kernel.org CE4EB60F6D Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=redhat.com Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=nongnu.org Received: from localhost ([::1]:58292 helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1mAXf6-0007UI-0H for qemu-devel@archiver.kernel.org; Mon, 02 Aug 2021 09:07:20 -0400 Received: from eggs.gnu.org ([2001:470:142:3::10]:33012) by lists.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1mAXbC-0000g8-22 for qemu-devel@nongnu.org; Mon, 02 Aug 2021 09:03:20 -0400 Received: from us-smtp-delivery-124.mimecast.com ([216.205.24.124]:48446) by eggs.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1mAXbA-0000Ph-Au for qemu-devel@nongnu.org; Mon, 02 Aug 2021 09:03:17 -0400 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1627909395; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=9d2/3bpDY1t4XsQxslnkCPrFxqCF7gn1s6shhmcNxcU=; b=hY66oLkxSnMrFJplxIRitJNv0TL3xs7CvwxKsJx8YJAHKnkGdMwjpOS8ksjpLmPcVnxFQ8 uipAOs5w1VuPzq6tifNcw08uv27XcxT3BV358bb3yCQbO2tIODptSxzjBs4e2P+HyHn91S DxusfhNVDJBFQ0lIaFjE4UzB5fImlGI= Received: from mimecast-mx01.redhat.com (mimecast-mx01.redhat.com [209.132.183.4]) (Using TLS) by relay.mimecast.com with ESMTP id us-mta-261-KybLuOVsMuay0RWlKOe9EQ-1; Mon, 02 Aug 2021 09:03:14 -0400 X-MC-Unique: KybLuOVsMuay0RWlKOe9EQ-1 Received: from smtp.corp.redhat.com (int-mx06.intmail.prod.int.phx2.redhat.com [10.5.11.16]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx01.redhat.com (Postfix) with ESMTPS id 8AEF81F6B2 for ; Mon, 2 Aug 2021 13:03:13 +0000 (UTC) Received: from localhost.localdomain.com (unknown [10.39.194.210]) by smtp.corp.redhat.com (Postfix) with ESMTP id 7F67317567; Mon, 2 Aug 2021 13:03:12 +0000 (UTC) From: =?UTF-8?q?Daniel=20P=2E=20Berrang=C3=A9?= To: qemu-devel@nongnu.org Subject: [PATCH 3/5] seccomp: fix blocking of process spawning Date: Mon, 2 Aug 2021 14:03:01 +0100 Message-Id: <20210802130303.3300108-4-berrange@redhat.com> In-Reply-To: <20210802130303.3300108-1-berrange@redhat.com> References: <20210802130303.3300108-1-berrange@redhat.com> MIME-Version: 1.0 X-Scanned-By: MIMEDefang 2.79 on 10.5.11.16 Authentication-Results: relay.mimecast.com; auth=pass smtp.auth=CUSA124A263 smtp.mailfrom=berrange@redhat.com X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: redhat.com Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Received-SPF: pass client-ip=216.205.24.124; envelope-from=berrange@redhat.com; helo=us-smtp-delivery-124.mimecast.com X-Spam_score_int: -34 X-Spam_score: -3.5 X-Spam_bar: --- X-Spam_report: (-3.5 / 5.0 requ) BAYES_00=-1.9, DKIMWL_WL_HIGH=-0.701, DKIM_SIGNED=0.1, DKIM_VALID=-0.1, DKIM_VALID_AU=-0.1, DKIM_VALID_EF=-0.1, RCVD_IN_DNSWL_LOW=-0.7, RCVD_IN_MSPIKE_H3=0.001, RCVD_IN_MSPIKE_WL=0.001, SPF_HELO_NONE=0.001, SPF_PASS=-0.001 autolearn=ham autolearn_force=no X-Spam_action: no action X-BeenThere: qemu-devel@nongnu.org X-Mailman-Version: 2.1.23 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: Eduardo Otubo , =?UTF-8?q?Daniel=20P=2E=20Berrang=C3=A9?= Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: "Qemu-devel" When '-sandbox on,spawn=deny' is given, we are supposed to block the ability to spawn processes. We naively blocked the 'fork' syscall, forgetting that any modern libc will use the 'clone' syscall instead. We can't simply block the 'clone' syscall though, as that will break thread creation. We thus list the set of flags used to create threads and block anything that doesn't match this exactly. Signed-off-by: Daniel P. Berrangé --- softmmu/qemu-seccomp.c | 101 ++++++++++++++++++++++++++++++++++++++ tests/unit/test-seccomp.c | 3 +- 2 files changed, 102 insertions(+), 2 deletions(-) diff --git a/softmmu/qemu-seccomp.c b/softmmu/qemu-seccomp.c index 9f6df8d033..57139cc9ce 100644 --- a/softmmu/qemu-seccomp.c +++ b/softmmu/qemu-seccomp.c @@ -46,6 +46,82 @@ const struct scmp_arg_cmp sched_setscheduler_arg[] = { { .arg = 1, .op = SCMP_CMP_NE, .datum_a = SCHED_IDLE } }; +/* + * See 'NOTES' in 'man 2 clone' - s390 & cross have 'flags' in + * different position to other architectures + */ +#if defined(HOST_S390X) || defined(HOST_S390) || defined(HOST_CRIS) +#define CLONE_FLAGS_ARG 1 +#else +#define CLONE_FLAGS_ARG 0 +#endif + +#ifndef CLONE_PIDFD +# define CLONE_PIDFD 0x00001000 +#endif + +#define REQUIRE_CLONE_FLAG(flag) \ + const struct scmp_arg_cmp clone_arg ## flag[] = { \ + { .arg = CLONE_FLAGS_ARG, \ + .op = SCMP_CMP_MASKED_EQ, \ + .datum_a = flag, .datum_b = 0 } } + +#define FORBID_CLONE_FLAG(flag) \ + const struct scmp_arg_cmp clone_arg ## flag[] = { \ + { .arg = CLONE_FLAGS_ARG, \ + .op = SCMP_CMP_MASKED_EQ, \ + .datum_a = flag, .datum_b = flag } } + +#define RULE_CLONE_FLAG(flag) \ + { SCMP_SYS(clone), QEMU_SECCOMP_SET_SPAWN, \ + ARRAY_SIZE(clone_arg ## flag), clone_arg ## flag, SCMP_ACT_TRAP } + +/* If no CLONE_* flags are set, except CSIGNAL, deny */ +const struct scmp_arg_cmp clone_arg_none[] = { + { .arg = CLONE_FLAGS_ARG, + .op = SCMP_CMP_MASKED_EQ, + .datum_a = ~(CSIGNAL), .datum_b = 0 } +}; + +/* + * pthread_create should always set all of these. + */ +REQUIRE_CLONE_FLAG(CLONE_VM); +REQUIRE_CLONE_FLAG(CLONE_FS); +REQUIRE_CLONE_FLAG(CLONE_FILES); +REQUIRE_CLONE_FLAG(CLONE_SIGHAND); +REQUIRE_CLONE_FLAG(CLONE_THREAD); +REQUIRE_CLONE_FLAG(CLONE_SYSVSEM); +REQUIRE_CLONE_FLAG(CLONE_SETTLS); +REQUIRE_CLONE_FLAG(CLONE_PARENT_SETTID); +REQUIRE_CLONE_FLAG(CLONE_CHILD_CLEARTID); +/* + * Musl sets this in pthread_create too, but it is + * obsolete and harmless since its behaviour is + * subsumed under CLONE_THREAD + */ +/*REQUIRE_CLONE_FLAG(CLONE_DETACHED);*/ + + +/* + * These all indicate an attempt to spawn a process + * instead of a thread, or other undesirable scenarios + */ +FORBID_CLONE_FLAG(CLONE_PIDFD); +FORBID_CLONE_FLAG(CLONE_PTRACE); +FORBID_CLONE_FLAG(CLONE_VFORK); +FORBID_CLONE_FLAG(CLONE_PARENT); +FORBID_CLONE_FLAG(CLONE_NEWNS); +FORBID_CLONE_FLAG(CLONE_UNTRACED); +FORBID_CLONE_FLAG(CLONE_NEWCGROUP); +FORBID_CLONE_FLAG(CLONE_NEWUTS); +FORBID_CLONE_FLAG(CLONE_NEWIPC); +FORBID_CLONE_FLAG(CLONE_NEWUSER); +FORBID_CLONE_FLAG(CLONE_NEWPID); +FORBID_CLONE_FLAG(CLONE_NEWNET); +FORBID_CLONE_FLAG(CLONE_IO); + + static const struct QemuSeccompSyscall denylist[] = { /* default set of syscalls that should get blocked */ { SCMP_SYS(reboot), QEMU_SECCOMP_SET_DEFAULT, @@ -143,6 +219,31 @@ static const struct QemuSeccompSyscall denylist[] = { 0, NULL, SCMP_ACT_TRAP }, { SCMP_SYS(execve), QEMU_SECCOMP_SET_SPAWN, 0, NULL, SCMP_ACT_TRAP }, + { SCMP_SYS(clone), QEMU_SECCOMP_SET_SPAWN, + ARRAY_SIZE(clone_arg_none), clone_arg_none, SCMP_ACT_TRAP }, + RULE_CLONE_FLAG(CLONE_VM), + RULE_CLONE_FLAG(CLONE_FS), + RULE_CLONE_FLAG(CLONE_FILES), + RULE_CLONE_FLAG(CLONE_SIGHAND), + RULE_CLONE_FLAG(CLONE_THREAD), + RULE_CLONE_FLAG(CLONE_SYSVSEM), + RULE_CLONE_FLAG(CLONE_SETTLS), + RULE_CLONE_FLAG(CLONE_PARENT_SETTID), + RULE_CLONE_FLAG(CLONE_CHILD_CLEARTID), + /*RULE_CLONE_FLAG(CLONE_DETACHED),*/ + RULE_CLONE_FLAG(CLONE_PIDFD), + RULE_CLONE_FLAG(CLONE_PTRACE), + RULE_CLONE_FLAG(CLONE_VFORK), + RULE_CLONE_FLAG(CLONE_PARENT), + RULE_CLONE_FLAG(CLONE_NEWNS), + RULE_CLONE_FLAG(CLONE_UNTRACED), + RULE_CLONE_FLAG(CLONE_NEWCGROUP), + RULE_CLONE_FLAG(CLONE_NEWUTS), + RULE_CLONE_FLAG(CLONE_NEWIPC), + RULE_CLONE_FLAG(CLONE_NEWUSER), + RULE_CLONE_FLAG(CLONE_NEWPID), + RULE_CLONE_FLAG(CLONE_NEWNET), + RULE_CLONE_FLAG(CLONE_IO), /* resource control */ { SCMP_SYS(setpriority), QEMU_SECCOMP_SET_RESOURCECTL, 0, NULL, SCMP_ACT_ERRNO(EPERM) }, diff --git a/tests/unit/test-seccomp.c b/tests/unit/test-seccomp.c index 10ab3e8fe5..3d7771e46c 100644 --- a/tests/unit/test-seccomp.c +++ b/tests/unit/test-seccomp.c @@ -126,8 +126,7 @@ static int doit_fork(void) static void test_seccomp_fork_on_nospawn(void) { - /* XXX fixme - should be killed */ - test_seccomp_passed("on,spawn=deny", doit_fork); + test_seccomp_killed("on,spawn=deny", doit_fork); } static void test_seccomp_fork_on(void) -- 2.31.1